This invention relates to a method and apparatus for expanding the width of a preformed fibrous web; and, more particularly, for expanding the width while maintaining original lengthwise fiber orientation and/or controlling the web profile.
Nonwoven webs of fibrous materials and nonwoven fabrics are commercially important materials in the textile and related industries. Nonwoven webs are formed from textile fibers or so-called "staple" fibers, such as cotton, wool, wood, jute, viscose rayon, nylon, polyester, or other materials varying in length from about one-fourth inch to about 2 or more inches. Such fibers are processed through conventional textile machinery. For example, a carding machine may be used to form a continuous length of rather two-dimensional, loosely associated fibers known as a carded web. These webs may be assembled to form a multiple layer or three-dimensional fibrous web of significant weight, e.g., from about several hundred grains to thousands of grains per square yard.
In continuous nonwoven fibrous webs, the textile fibers are arrayed at various angles to the lengthwise axis of the web. Depending upon processing techniques, the fibrous webs may be oriented, that is parallelized, or isotropic. When a web is formed by the action of a carding machine, the fibers are usually predominantly oriented in the machine direction, i.e., the lengthwise axis of the fibrous web, which is the direction in which a web is formed and is moved continuously and assembled with other webs of similar fiber orientation. On the other hand, isotropic webs may be formed such as by air-laying.
Carding or air-laying machines produce somewhat standardized fibrous web widths and it becomes necessary usually at some stage in processing to vary these widths either simply to obtain a particular width or for the purpose of efficiency, among other purposes. Many apparatuses and methods are known to the art for expanding the width of a nonwoven fibrous web including the use of bowed rollers, springs, cross-stretching belts, diverging disks, and the like. All of these apparatuses and methods have disadvantages including among other things the need for complicated and expensive equipment, the inability to expand the width of the web without either altering the orientation of the fibers or weakening the web, and the inability to control and change the profile of web, i.e., the thickness, uniformity, and weight of the web across its width.